(1) Field of the Invention
The present invention relates to a ball bearing slide unit for linear motion wherein said slide unit is mounted on a track rail of rectangular cross section. The track rail is provided with symmetrical linear track surfaces at both vertical side surfaces, and the slide unit is provided with track surfaces opposing said track rail track surfaces and has linear return holes running parallel to said track surfaces, coupled with direction changing paths which connect both ends of said track surfaces and said return holes, and is further formed with circulating paths where a group of balls endlessly circulate while supporting a load and rolling between said both track surfaces.
(2) Description of Prior Art
In a prior art ball bearing unit for linear motion as shown in FIG. 14, 4 sets of circulating paths 130, 131, 132, 133 for groups of balls were provided at left, right, upper and lower sides, and thus, the height and width of the slide unit 135 was large compared with the track rail 134, and also cost was high, and therefore there was a demand for a more compact slide unit.
In another prior art example, as shown in FIG. 15, slide unit 137 is mounted on the inclined side surfaces of the track rail of trapezoidal shape. The circulating paths were reduced to two sets, as shown by 138, 139. Thus the compactness of the slide unit 137 was achieved. However, although said slide unit 137 can support a downward load from above without trouble, it is not usable for an upward load from below such that will raise the slide unit 137, and thus, there was a limitation to its application.
Also, as shown in FIG. 16, when mounting the attached body 121 on the prior art slide unit, the top surface of the slide unit 120 was finished so as to serve for the mounting surface. and Female threaded bores 122 were provided at accurate required positions on said top surface for fastening the attached body 121. The construction was the so-called top fastening one which allowed fastening of bolts 123 from above the slide unit 120. When it was required to fasten the attached body 124 from below the slide unit 120, as shown in FIG. 17, guide holes 126 were provided at accurate required positions to guide and fit bolts 125 from below, the bolts being threaded aligned female threaded bores in said body 124, resulting in a bottom fastening arrangement. Thus, for bolt fastening from either above or below, it was necessary to drill the respective bolt holes separately at accurate positions. If an attempt was made to provide a ball bearing capable for both top fastening and bottom fastening, the number of machining operations increased and the size of the slide unit increased in proportion to the increase in the number of drilling positions, and as a result, the entire size of the attached body including the slide unit 120 became large, and this was contrary to the demand for a smaller and a lighter slide unit.
To avoid the above disadvantage, it was necessary to manufacture two kinds of slide units, one having female threads for top fastening and the other having bolt guide holes for bottom fastening, said female threads and said guide holes being at the same positions for the same type slide unit. This caused an increase in stock and an increase in cost, and a solution for this situation was desired.